Field of the Invention
The present invention relates to control apparatus for a vibration type actuator.
In general, a vibration type actuator, such as a vibrating wave motor or the like, has a vibration member in which driving vibration is generated, and a contact member in press contact with the vibration member; the driving vibration generated in the vibration member causes relative movement between the vibration member and the contact member.
The vibration member typically is composed of an elastic member and a piezoelectric element, which functions as an electro-mechanical energy conversion element. For example, piezoelectric elements with driving phases placed at positions with a spatial phase difference of 90° relative to the elastic member may be configured so that alternating signals of two phases with a phase difference of 90° may be applied to the two driving phases so as to form respective bending vibrations on the elastic member. In this manner a traveling wave is generated in the vibration member by composition of these bending vibrations, and the contact body pressed against the vibration member is driven with a driving force by frictional contact therebetween.
A frictional material for obtaining the appropriate frictional force is bonded, applied, or formed on contact portions of the vibration member and the contact member.
The elastic member forming the vibration member is made of a material such as aluminum or the like, having a poor vibration damping property, i.e., a material resistant to damping of vibration.
In a vibration type actuator of this type, a variety of control operations can be implemented by altering the phase difference between the alternating signals of the two phases applied.
In the control apparatus for the vibration type actuator described in Japanese Patent Application Laid-Open No. 63-209478, the driving voltages applied in a stop operation are reversed in phase (forwarded or retarded by 180°) to hasten the stop operation. In the control apparatus for the vibration type actuator described in Japanese Patent Application Laid-Open No. 2-206373, voltages in a phase relation to reverse the rotation in the stop operation are applied to hasten the stop operation.